The invention relates to an electrical machine with a machine housing receiving an electrically excited rotor and a stator of the electrical machine and with an electronics unit fastened to the machine housing and electrically connected to an exciter winding of the rotor via at least one sliding contact consisting of at least one slip ring assigned to the rotor and at least one brush assigned to the electronics unit, the brush being arranged displaceably in a brush holder.
Electrical machines of the type mentioned at the beginning are known from the prior art. The electrical machine has the rotor and the stator, which are arranged at least partly in the machine housing. The electrical machine is activated by means of the electronics unit. This means that it is electrically connected to the rotor and/or the stator of the electrical machine, in order to feed electrical current to the exciter winding of the rotor and/or an exciter winding of the stator. Because the rotor rotates with respect to the machine housing, and consequently the electronics unit, during the operation of the electrical machine, the electrical connection between the electronics unit and the rotor is established via the sliding contact. This sliding contact consists of the at least one slip ring and the at least one brush. The slip ring is in this case assigned to the rotor and is provided for example on a rotor shaft, on which the rotor is also arranged to rotate therewith. The brush on the other hand is arranged in the electronics unit and is consequently usually fixed in place.
The sliding contact between the brush and the slip ring causes wear, in particular of the brush. The brush is therefore displaceable, at least in the radial direction—with respect to a longitudinal axis of the electrical machine or an axis of rotation of the rotor. The brush is usually urged in the direction of the slip ring by means of a spring element. In this way, the wear of the brush can be compensated. The brush is arranged displaceably in the brush holder. It is preferably arranged in the brush holder in such a way that it is movable only in the radial direction, that is to say in particular toward the slip ring. The brush holder is usually connected to the electronics unit in a fixed and unreleasable manner. During assembly of the electrical machine, the electronics unit is fastened by three screws directly to the machine housing, in particular a bearing plate of the machine housing.
Known for example from the prior art is DE 10 2004 004 745 A1. This shows a brush holder for an electrical machine which has a stator and a rotor. The brush holder has four receiving shafts for a plurality of carbon brushes. It is intended that all four receiving shafts are fitted with a carbon brush and that the carbon brushes are switched as pairs in parallel.
On account of the wear, it is necessary from time to time to exchange the brush. However, due to the permanent fastening of the brush holder to the electronics unit described above, it is necessary always to exchange the entire electronics unit together with the brush holder. This makes the exchange of the brush complicated and costly.